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IS 9527-1 (1981) : Code of practice for design and
construction of port and harbour structures, Part 1:
Concrete monoliths [CED 47: Ports and Harbours]
Jawaharlal Nehru
'Step Out From the Old to the New'
■K^y / 1 juaaaws^fea rs^^TTF^
2*S< W I *>S*V2^NK^
^frcvvv^
Satyanarayan Gangaram Pitroda
Invent a New India Using Knowledge
?TR TJ^ ^TT teMHI | ^t ^Wt ^m\ ^f ^TT ^T^?TT \'
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"Knowledge is such a treasure which cannot be stolen"
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•
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*rt*2V^
PROTECTED BY COPYRIGHT
IS : 9527 { Part I ) - 1981
(Reaffirmed 2012)
Indian Standard
CODE OF PRACTICE FOR DESIGN AND
CONSTRUCTION OF PORT AND
HARBOUR STRUCTURES
PART I CONCRETE MONOLITHS
UDC 627 33 i 62404 ; 693 5 : 006- 76
*<^ *
ff
© Copyright 1982
INDIAN STANDARDS INSTITUTION
MANAK BHAVAN, 9 BAHADUR St I AH ZAFAR MARC
SEW DELHI ItGMK
r8
IS : 9527 ( Part I )- 1981
Indian Standard
CODE OF PRACTICE FOR DESIGN AND
CONSTRUCTION OF PORT AND
HARBOUR STRUCTURES
PART I CONCRETE MONOLITHS
Ports and Harbours Sectional Committee, BDC 66
Chairman Representing
Shri H. R. Laxminarayan Ministry of Shipping and Transport
Members
Shri T. R. Subramanyam ( Alternate to
Shri H. R. Laxminarayan )
Shri M. Balasubramaniam Mormugao Port Trust, Vasco-Da-Gama
Gapt P. N. Batra Marine Department ( Calcutta Port Trust ), Calcutta
Capt D. K. Dutta ( Alternate )
Shri N. P. Bhakta Pre-Investment Survey of Fishing Harbour, Bangalore
Shri H. V. Ramaswamy ( Alternate )
Shri R. K. Budhbhatti Public Works Department, Government of Gujarat,
Ahmadabad
Shri B. P. Kukadia ( Alternate )
Chief Engineer Chief Engineer's Department ( Calcutta Port Trust ),
Calcutta
Chief Ports Officer Maharashtra State Port Authority, Bombay
Coastal Engineer ( Alternate )
Director Central Water Commission, New Delhi
Chief Research Officer I ( Alternate )
Shri A. H. Divanji Asia Foundation & Construction Pvt Ltd, Bombay
Shri A. N. Jangle ( Alternate )
Shri K. K. Framji Consulting Engineering Services India Pvt Ltd,
New Delhi
Shri S. Ghosh ( Alternate )
Shri S. R. Gattonde Bombay Port Trust, Bombay
Shri Hasmukh P. Oza In personal capacity ( Atul, 20 Pathik Society,
Ahmadabad )
Shri A. I. Ibrahim Continental Construction Pvt Ltd, New Delhi
Shri S. P. Rao Janamanchi Oil and Natural Gas Commission, Dehra Dun
Shri P. K. Kandaswamy Engineering Department ( Madras Port Trust ),
Madras
Shri M. R. Selvaraj ( Alternate )
( Continued on page 2 )
© Copyright 1982
INDIAN STANDARDS INSTITUTION
This publication is protected under the Indian Copyright Act ( XIV of 1957 ) and
reproduction in whole or in part by any means except with written permission of the
publisher shall be deemed to be an infringement of copyright under the said Act.
IS t 9527 ( Part I )- 1981
( Continued from page 1 )
Members
Capt R. D. Kohu
Capt G. A. Mande
Capt V. K. Kapur ( Alternate )
Capt M. V. K. Menon Cochin Port Trust, Cochin
Capt Abraham Kuruvilla ( Alternate )
Representing
Shipping Corporation of India* Bombay
Marine Department ( Madras Port Trust )
Madras
Hydraulic Study Department ( Calcutta Port Trust ),
Calcutta
Project & Equipment Corporation of India Ltd,
New Delhi
Indian Institute of Technology, Bombay
Karnataka Regional Engineering College, Srinivas-
nagar
Engineer-in-Chief s Branch, Army Headquarters
Hindustan Construction Co Ltd, Bombay
Dr S. K. Nag
Dr A. N. Biswas ( Alternate )
Shri H. Nandi
Prof S. Narasimhan
Dr I. V. Nayak
Prof G. Ranganna ( Alternate )
Brig Ombir Singh
Shri B. K. Panthaky
Shri P. V. Naik ( Alternate )
Shri G. Raghavan Andaman Lakshadweep Harbour Works, New Delhi
Shri M. Gopalakrishnan ( Alternate )
Rear Admiral K. T. Raju Indian Navy ( Ministry of Defence ), Vishakhapatnam
Lt-Col J. R. Taneja ( Alternate )
Shri T. V. Ramana Rao Visakhapatnam Port Trust, Vishakhapatnam
Shri S. R. Roessler HOWE ( India ) Pvt Ltd, New Delhi
Shri C. S. Debke ( Alternate )
Capt Subimal Mookerjee
Cdr P. P. Sivamani ( Alternate )
Superintending Engineer
( Central Mechanical Circle )
Senior Deputy Chief Engineer
( Bldgs ) ( Alternate )
Shri M. C. Tandon Stup Consultants Ltd, Bombay
Shri M. .K. Chatterjee ( Alternate )
Dr V. D. Tapasvi Engineers India Ltd, New Delhi
Shri M. Chowdhury ( Alternate )
Shri G. Raman, Director General, ISI ( Ex-qfficio Member )
Director ( Civ Engg )
Secretaries
Shri K. M. Mathur
Deputy Director ( Civ Engg ), ISI
Shri M. N. Neelakandhan
Assistant Director ( Civ Engg ), ISI
Indian Navy ( Operational ), Ministry of Defence
Public Works Department, Government of Tamil
Nadu, Madras
IS : 9527 ( Part I ) - 1981
Indian Standard
CODE OF PRACTICE FOR DESIGN AND
CONSTRUCTION OF PORT AND
HARBOUR STRUCTURES
PART I CONCRETE MONOLITHS
0. FOREWORD
0,1 This Indian Standard ( Part I ) was adopted by the Indian Standards
Institution on 31 July 1981, after the draft finalized by the Ports and
Harbours Sectional Committee had been approved by the Civil Engineering
Division Council.
0.2 This standard pertaining to waterfront structures is being, issued in the
following parts:
Parti
Concrete monoliths
Part II
Caissons
Part III
Sheet piles
Part IV
Cellular sheet pile structures,
0.3 The methods of design and construction of monoliths for ports and
harbours are normally used on the production of evidence of the adequacy
of such methods based on analysis, model tests, and past experience. In
this code, an attempt has been made to cover common methods of design
and construction of concrete monoliths for port and harbour structures.
0.4 Monolith is a large hollow rectangular or circular foundation sunk
as an open caisson. It may have several pockets /wells. On reaching the
desired founding strata, the bottom of the pocket/pockets is invariably
plugged with concrete and the remaining portion often filled with sand
or mass concrete. Monoliths are constructed of concrete, steel, masonry
or timber; the most common being concrete. Timber monoliths, though
extensively built in the past are now only of academic interest. Monoliths
of required shape are built in stages on dry ground and sunk into the
ground. The bottom-most portion is fixed with the cutting edge and is
placed on the surface of the ground where the monolith is desired to be
sunk. This code deals with only concrete monoliths which are largely and
commonly used for the construction of marine structures such as quaywalls,
dolphins and jetties.
IS : 9527 ( Part I ).- 1981
0.5 Monoliths arc most suitable for foundation in waterfront structures
where the predominating soil consists of soft clay, silt, sand or gravel.
These subsoil materials can be readily excavated by grabbing from the
pockets and they do not offer high skin friction during sinking. The mono-
liths may not be suitable where the sinking is through very hard strata,
sunken barges, large boulders, tree trunks and other obstacles. By the process
of grabbing under water, the soil around the monolith gets loose and tends
to flow inside the pocket/pockets and thus cause subsidence of the ground
around the monolith. Where damage may be caused by such subsidence
to existing structures, the construction of monoliths may not be advisable.
0.6 The monoliths are subjected to a variety of determinate and indeter-
minate forces. Moreover the saline waters, tidal variations, and the chemical
effects of transhipped and stored goods also severely attack the building
materials used in the construction. Therefore, the design of the monolith
structure only on the static principles would be inadequate. The design
shall be such that the dangers of fatigue, excessive wear and abrasion,
corrosion and rusting, cracks, etc, are as minimum as possible.
0.7 From the view point of basic requirements, the structure should be
stable, strong, functionally efficient, and economical. For this purpose,
the structural system is first chosen and the loads on it are established.
The state of stress is then determined at each of its points under any and
all possible loads. The calculated stresses are then compared with stresses
that the materials can safely stand.
0.8 During sinking through soft strata which offers low skin friction, the
monolith at times drops down suddenly when the cutting edge is cleared.
If the soft strata is overlain by stiff strata, that is when the strata near
the top of the monolith offers skin friction greater than the weight of the
monolith, the monolith gets suspended from the top and is restrained from
the sudden drop. The steining at such occasions is subjected to severe
tension and breaks. To safe-guard against such eventualities, adequate
reinforcement shall be provided.
0.9 In the formulation of this standard, due weightage has been given
to international coordination among the standards and practices prevailing
in different countries in addition to relating it to the practices in the field
in this country.
0.10 For the purpose of deciding whether a particular requirement of this
standard is complied with, the final value, observed or calculated, expressing
the result of a test, shall be rounded off in accordance with IS : 2-1960*.
The number of significant places retained in the rounded off value should
be the same as that of the specified value in this standard.
*Rules for rounding off numerical values ( revised ) .
4
IS : 9527 ( Part I )- 1981
1. SCOPE
1.1 This standard ( Part I ) covers the design and construction of concrete
monoliths for port and harbour structures.
2. TERMINOLOGY
2.0 For the purpose of this standard, the definitions given in IS : 7314-1974*
and the following shall apply.
Note — Various elements of a typical concrete monolith are illustrated in Fig. 1 .
2.1 Bottom Plug — The open bottom of the monolith is sealed with
concrete when it is sunk to the designed founding strata. This sealed base
is called the bottom plug, and is meant to evenly transfer the vertical load
to the founding strata; it is also termed as bottom seal.
2.2 Cover Slab — The slab constructed on the monolith steinings to cover
the pocket/pockets.
2.3 Gutting Edge — The lowermost portion of the monolith which cuts
into the soil during sinking. It is generally made of structural steel,
2.4 Deck-Slab — The slab built at the deck level covering the whole
monolith in plan.
2.5 Dewatering — The removal of water from monolith pocket/pockets
by pumping or by any other means.
2.6 Fascia Wall — Sea-ward wall of the waterfront structure against
which the vessels are berthed.
2.7 Filling — The material filled inside the monolith pocket/pockets.
This is primarily done to improve the stability of the monolith, but in
certain cases done to reduce the stresses in the steining.
2.8 Kentledge — The load placed on the monolith to aid sinking. It may
be scrap metal, large stones, tanks filled with water, or any other convenient
material
2.9 Kerb — The lowermost tapering portion of the steining provided to
facilitate sinking. It is heavily reinforced and fitted with cutting edge at
the bottom.
2.10 Monolith — A large hollow rectangular or circular structure built
in stages at the ground level and then sunk to the desired depth by exca-
vation. It may have one or more pockets/wells/dredge holes.
♦Glossary of terms relating to port and harbour engineering.
IS ; 9527 ( Part I ) - 1981
REINFORCED CONCRETE
PAVING
CONSTRUCTION JOINT
OREUGEO
LEVEL
\ FILLING
/
FILLING
X
-REINFORCED
CAP SLAB ^ SUPERSTRUCTURE
-POCKET/WELL/OREOGEO HOLE
-DIAPHRAGM WALL
/-STfilNtNG
/ (INSIDE)
>-STElNIN&
/ (OUTSIDE!
-KERB
: BOTTOM PLUG
Fig. 1 Various Elements of a Monolith
6
IS : 9527 ( Part I ) - 1981
2.11 Pocket, Well or Dredge Hole — Vertical shaft between the steining
of a monolith through which soil is excavated. The removal of the soil
through the pocket/well/dredge hole makes the monolith sink into the
ground.
2.12 Cantilever Relieving Platform — A cantilever platform sometimes
built on the land side of the monolith, at suitable depth, to relieve
excessive overturning moments caused by lateral forces.
2.13 Sand-Blow — The sudden flow of the soil from the areas adjacent
to the steining of the monolith into the dredge hole/pocket.
2.14 Service Galleries or Ducts — The ducts constructed between the
deck slab and the cover slab. These are meant to install the required
services for the vessels berthed alongside.
2.15 Shift — The net horizontal movement of the monolith which may be
due to tilt during or after construction from its designed position at a
given level.
2.16 Steining — The load bearing wall of the monolith, external as well
as internal, if any.
2.17 Tilt — Inclination that the monolith may acquire with respect to
the vertical axis expressed as the tangent of the angle measured from the
founding level.
3. MATERIALS
3.1 The materials used in the construction should conform to the require-
ments laid down in IS : 456-1978*.
3.2 Plums — In mass concrete members, stone plums of 1 60 to
300 mm size or any other reasonable size may be used in plain concrete
work up to a maximum limit of 20 percent by volume of concrete when
specially permitted.
3.2.1 All plums shall be hard, durable, clean and free from soft materials
or loose pieces or deleterious substances embedded in them and shall not
have sharp corners.
3.3 Storage of Materials — Storage of materials shall be as per
IS :4082-1977t.
*Gode of practice for plain and reinforced concrete ( third revision).
f Recommendations on stacking and storage of construction materials at site (first revision ) .
IS : 9527 ( Part I )- 1981
4. STRUCTURAL DESIGN
4.1 Dimensions and Shapes
4.1.1 There is no ideal solution for the design of a monolith and the
final design is a compromise of a number of conflicting requirements.
The shapes in plan may be round, oblong, oval, rectangular, square,
hexagonal, etc and may have one or more cells/pockets ( see Fig. 2 ) .
The ideal shape of a monolith is circular in plan as this offers minimum
surface area to the skin friction due to surrounding soil which opposes the
sinking. The shape in most cases is dictated by the following:
a) Requirements of the superstructure, namely crane tracks;
service galleries, and other fixtures on the monoliths;
b) The magnitude of earth and hydrostatic pressures;
c) The bearing capacity of the subsoil;
d) The magnitude of horizontal and vertical loads acting on the
monolith;
e) The requirements of control over tilt and shifts during sinking;
f ) The sinking effort to sink the monolith to its required founding
level ; and
g) The dimensions of equipment available for sinking of monoliths.
4.1.2 The verticality of the monolith, while sinking is better controlled
by adopting a shape which comprises multiple pockets/wells. The pockets
shall be symmetrically disposed in both sides of the axis to achieve control
on tilting in both the directions (Fig. 2A and 2B). However, at corners
of turnings or restricted locations narrower shape of monoliths may have
to be used adopting a row of pockets ( Fig. 2G and 2D). In such cases
care shall be taken to provide pockets of suitable size so that the grab could
effectively work for the sinking of monolith. It is advisable to keep the size
of the pocket not less than 3 x 3 m as far as possible.
4*2 Design Loads
4.2.1 Permanent Loads
4.2.1.1 The permanent loads are the maximum vertical and lateral
loads acting on a monolith after it is constructed and sunk in place.
4.2.1.2 IS : 4651 (Part III )-1974* covers the magnitude of the
forces and the loads on water front structures which include monoliths.
*Code of practice for planning and design of ports and harbours: Part III Loading
(first revision ) .
IS : 9527 ( Part I ) - 1981
CD
CD
CD CD
ODDO
DDDD
2A
2B
/ \ / \
\ * K r
2C
2D
i
N I /
2E 2F
Fig. 2 Typical Shapes of Monolith
4.2.1.3 The earth pressure on a monolith shall be computed as stipu-
lated in IS : 4651 ( Part II )~1969*. Earth pressures and the average soil
properties as given in Table 1 may be used for preliminary designs, whereas
the final design shall be based on the soil properties obtained from the
soil tests.
4.2.1.4 The wind and seismic forces shall be taken conforming to
IS : 875-1964f and IS : 1893-1975J respectively.
*Code of practice for planning and design of ports and harbours: Part II Earth pressures.
fGode of practice for structural safety of buildings: Loading standards {revised).
^Criteria for earthquake resistant design of structures {third revision).
IS : 9527 ( Part I ) - 1981
TABLE 1
AVERAGE SOIL PROPERTIES
{Clause 4.2.1.3)
Type of Soil
Bulk Density
Angle of
Cohesive
Coefficient
A
Internal
Friction
Strength
cwt
(
Above
Sub-
Compressi-
Water
merged
bility
(i)
(2)
(3)
W
(5)
(6)
*/m 3
tjm 3
degree
tjm 2 -
t/m 2 X 10 3
J\fon-cohesive Soils
Loose sand, round
1-8
l'O
30
—
2-5
Loose sand, angular
1*8
1*0
32'5
_—
4-8
Medium dense sand,
round
1*9
1-1
32*5
—
5-10
Medium dense sand,
angular
19
1*1
35
—
8-15
Gravel without sand
1-6
1*0
37*5
___
10-15
Coarse gravel, sharp edged
1-8
1*1
40
—
15-20
Cohesive Soils
Soft clay
1*7
0*7
0-17*5
P4
0*1-0*25
Medium stiff clay
1-9
0*9
25
25
0*5-P0
Stiff clay
1*8
0*8
20
2
0*25-0*5
Boulder clay, solid
2'2
1*2
30
2*5
3*0-10*0
Loam, semifirm
2*1
PI
27*5
1
0*5-2
Loam, soft
P9
0*9
27*5
—
0*4-0*8
Silt
1-8
0*8
27-5
„
0*3-1
Soft, organic, slightly
1*7
0*7
20
1
0-2-0*5
clayey sea silt
Peat
11
0*1
15
0*5
0*04-0*1
4.2,1,5 A gap is left between the adjacent monoliths to accommodate
for tilts and shifts. This gap shall not be less than two times the thickness
of steining. The ultimate closure of gap will result in the transference of
the lateral force into the monolith. The computed lateral force on a monolith
has to be proportionately increased to account for this transference.
4.2.2 Temporary Loads
4.2.2.1 A monolith is also likely to be subjected to large stresses during
the construction period.
4.2.2.2 A monolith may be hung up near the top due to skin friction.
The lower portion of the monolith is then subjected to tension.
4.2.2.3 A monolith may get supported on one side only or on two
opposite corners only, when it meets with an obstacle/obstacles.
4.2*2.4 During a sand-blow or during the conditions like sudden drop
that may occur at the site during sinking, the monolith is subjected to high
earth and hydrostatic pressures.
10
IS : 9527 ( Part I ) - 1981
4.2.2.5 Monolith, during sinking, invariably tilts and shifts. The
measures adopted for the rectification of the tilts and shifts impose large
vertical and raking forces and high earth pressures.
4.2.3 Skin Friction — Skin friction is the shearing resistance between the
soil and the exterior surface of the monolith encountered during the process
of sinking. The skin friction shall be assessed on the basis of soil properties.
4.3 Permissible Stresses
4.3.1 The permissible stresses in concrete and steel reinforcement shall
be the same as those given in IS : 456-1978* unless otherwise specified.
4.4 Steining
4.4.1 The thickness of steining shall be fixed from the following considera-
tions :
a) The steining should be able to withstand the stresses caused
by the temporary loads during sinking besides the permanent
loads.
b) It should normally be possible to sink the monoliths without
the use of excessive kentledge.
Note — For different thicknesses of steinings and shapes of the monolith, the
sinking effort should be evaluated and whichever combination gives the higher
value may be adopted for design. The sinking effort is defined as the ratio between
the weight of the monolith and its surface area. The use of kentledge cannot be
completely avoided in stiffer stratas. However, the designer may decide between
the use of thicker steining or application of kentledge.
4.4.2 For preliminary designs, the thickness of steining may be chosen
from the following thumb rule:
\ 100 c 2 J
where
t = thickness of the steining,
H = designed depth of the monolith,
L — maximum unsupported length in case of rectangular
monolith and the external diameter in case of circular
monolith, and
Q and C 2 = constants which depend upon the type of strata
through which the monolith is expected to be sunk;
values of these constants are given in Table 2.
The thickness of the concrete steining shall not be less than 450 mm.
*Code of practice for plain and reinforced concrete ( third revision ).
11
IS : 9527 ( Part I ) - 1981
TABLE 2 CONSTANTS C x AND d FOR CALCULATING THE THICKNESS
OF THE STEINING
( Clause 4.4.2 )
Strata Constants
C x C z
0) (2) (3)
Sand 1-0 10
Soft clay 1*1 10
Hard clay 1*25 10
Boulders , Kankar, shale and 1*25 8
such hard material
4.4.3 The exterior walls of a monolith are designed to withstand the
flexural stresses caused by the combined maximum lateral pressure and
the compressive stress caused by the vertical load including the weight of
the monolith. The connections between the interior and exterior walls
shall be sufficiently rigid for the mutual transference of the loads coming
on them.
4.4.4 Having chosen the preliminary thickness of the steining the actual
stresses which are likely to occur at site shall be worked out to arrive at the
final thickness and the reinforcements. The final thickness shall, however,
not be less than that stipulated in 4.4.2. The circular monolith is generally
subjected to compressive stresses due to vertical loads as well as earth and
hydrostatic pressures acting from outside. The behaviour of stresses in the
case of rectangular monoliths is different as the steining is under direct
compression due to vertical loads and subjected to bending stresses due to
external earth and hydrostatic pressures. In the case of rectangular mono-
liths with multiple wells/pockets, the stresses shall be checked for the follow-
ing conditions:
a) The monolith has not reached the desired founding strata
but is very close to it; to facilitate sinking at this stage, kentledge
is used and the pocket/pockets are dewatered fully or partly.
b) In the completed state of the monolith where full passive earth
pressure and active earth pressure are mobilised on the sea-side
steining and the land-side steining respectively.
Note — It is, however, advisable to adopt the same thickness of steining throughout
the depth, and the reinforcement may be altered to suit the varying stresses.
4.4.5 Reinforcement — The vertical and horizontal reinforcement shall
be provided according to the stresses worked-out at different depths. Where
the computed stresses are within permissible stresses of the concrete, nominal
reinforcement as specified in IS : 456-1978* shall be provided.
♦Code of practice for plain and reinforced concrete ( third revision ).
12
IS j 9527 ( Part I ) - 1981
4.5 Kerb
4.5.1 The kerb is made of reinforced concrete. The depth of the kerb
is governed by the thickness of the steining and the inclination provided
to the inner face of the steining. In general, the requirements of a kerb are
as follows:
a) It should be strong enough to transmit the loads to the bottom
of the plug.
b) The width of the base of the kerb should be such that it affords
low resistance when the well is being sunk through hard
material and should provide necessary stability in the case of
soft material.
c) The slope of the inner faces of the kerbs should be such as to
push forward easily the soil into the dredger hole/pocket.
Generally the angle should be decided to suit the dominant
factor in sinking. Whether soft soil at the early stages or stiff
or bouldering soil at the later stages, the inclination of the
inner face with respect to the vertical is recommended between
30° and 45° depending upon the type of strata. In the case of
stiff clays, an angle of 30° and in the case of sands or soft clays,
an angle of 45° are preferred.
d) A small offset on the outside is to be provided to ease sinking.
4.5.2 The kerb shall be designed for the greater of the resultant hori-
zontal forces computed in the following cases:
a) when the monolith is being sunk, and
b) when the kerb is resting on the bottom plug.
In case of (b), it may be reasonable to consider the active earth
pressure around the kerb particularly in granular soil while computing
the horizontal force.
4.5.3 The forces acting on a kerb are the following and have been illustra-
ted in Fig, 3:
a) Weight of the steining and the temporary vertical loads per
metre width ( W ) ,
b) Reaction acting normal to the bevel face of the kerb per unit
width ( JV),
c) Tangential force acting on the bevel face per unit width
(.S=ftXJV, where ft is the coefficient of friction between the
soil and the kerb), and
d) Resultant horizontal force on the kerb per unit width (//).
13
IS : 9527 ( Part I ) - 1981
JV and H may be computed as the reactions from the bottom pmg"
by any of the standard methods recommended in the textbooks.
Note — The symbols indicated in the figure have been described in 4.5.3 and 4.5.4.
Fig. 3 Forges on a Kerb
4,5.4 The horizontal thrust, H, causes:
a) moment, M, at the junction of the kerb and the steining,
M— iJx^/2, where dj2 is lever arm as shown in Fig. 3; and
b) hoop tension in case of circular monolith or tension on the
sides of kerb which are parallel to the direction of H in case
of rectangular monolith.
Adequate reinforcement shall be provided to take care of the
resultant stresses.
14
IS : 9527 ( Part I ) - 1981
4.5.5 The reinforcement in the kerb shall be designed to meet the require-
ments given in 4*5.3. It is also desirable to make provision for increased
stresses due to temporary load such as sudden dropping of the well, by
increasing the calculated tension reinforcement by 50 percent and by
providing vertical bond rods. The reinforcement may be arranged in the
form as shown in Fig. 4.
In case of rectangular monoliths, the reinforcing bars provided to
resist the pull, shall be anchored properly round the corners to resist splitting.
4A OUTSIDE KERB 4B INSIDE KERB
Fig. 4 Typical Arrangement of Reinforcement in Kerbs
4.6 Gutting Edge
4.6.1 The cutting edge is made of structural steel plates and angles as
it is subjected to concentrated high stresses while sinking; it shall be extre*
mely strong, and rigidly and adequately anchored to the kerb.
15
IS : 9527 ( Part I )- 1981
4*6*2 The cutting edge projecting from the kerb face shall be capable
of taking the bending stresses caused while correcting the well for any tilt
or shift.
4.6.3 The cutting edges shall be fabricated with a sharp edge or with a
stub nose as shown in Fig. 5A stub nose is to be preferred in soft clay and a
sharp edge in stiff clay or granular soils.
5A OUTSIDE CUTTING EDGE
5B OUTSIDE CUTTING EDGE
5C INSIDE CUTTING EOGE
Fig. 5 Gutting Edges
4.6*4 The cutting edge fixed to the kerb of the inside steining may be
kept about 300 mm higher than the cutting edge of the outside steining
to avoid rocking of the monoliths during sinking.
16
IS : 9527 ( Part I ) - 1981
4.7 Bottom Plug
4.7.1 The bottom plug is the permanent base transmitting the loads
of a monolith on to founding strata and shall, therefore, be designed accord-
ingly. When it is anticipated to dewater the pockets of the monolith after
its bottom is plugged, it shall be ensured that the bottom plug is adequately
designed, constructed and cured so that it is able to withstand the stresses
due to the uplift. It may be designed as a spherical dome or a thick flat
slab supported on all sides by the steining and loaded by the subgrade
reaction as a uniformly distributed load ( Fig. 6 ) . The spherical form is
more commonly adopted as compared to flat slab because of being more
efficient.
4.7.2 If the bottom plug is constructed as a flat arch, that is, the rise is
very small as compared to the span, the thickness of the plug can be found
out using the following expression ( see Fig. 6C ) :
8kc
where
t = thickness of the bottom plug in m,
q = intensity of contact soil pressure or hydrostatic
pressure per unit area in N/m 2 ,
/ = span in m,
h — rise in m, and
f c = permissible compressive stress in concrete of the
bottom plug in N/m 2 .
4.7.3 The thickness of the bottom plug may also be worked out by
applying the principles of theory of elasticity. For circular and rectangular
monoliths, with different support conditions, the thickness of bottom plug
may be worked out from the expressions given in Tables 3 and 4.
4.7.4 Alternatively, the thickness of the bottom plug may be provided
empirically as 0'3 m more than the thickness of the kerb.
4.8 Cover Slab
4.8.1 The cover slab is designed to span the pockets/wells of the monolith.
The slab is supported by the steinings on all the four sides, and is loaded
by the superstructure and surcharge acting on the monolith structure.
The support, if any offered by the sand filling in the pockets is ignored in
17
IS : 9527 ( Part I )- 1981
6A ARCH/ DOME SHAPED BOTTOM PLUG
6B FLAT BOTTOM PLUG
-* Ft
STE1NING
NORMAL
THRUST ON
THE BOTTOM
PLUG
6C DESIGN OF BOTTOM PLUG AS A
FLAT ARCH
Note — The symbols indicated in Fig. 6C are described in 4.7.2.
Fig. 6 Bottom Plugs and Their Design
18
IS : 9527 ( Part I ) - 1981
TABLE 3 THICKNESS OF BOTTOM PLUG
(Clause 4.7.3)
Support Condition Thickness
Circular Monolith Rectangular Monolith
(1) (2) (3)
m m
6 flqP
I 3q R* (3 + /A ) /
Edges simply supported A / — _ A /
/ W1JT& 6 « qP
Edges fixed
8/c /c
Note 1 — In the expressions given in the table, q,f c and / are same as in 4.7,2;
R is the radius of the monolith in m; fl is Poisson's ratio; and « and £ are coeffi-
cients given in Table 4.
Note 2 — The permissible stress in the bottom plug concrete may be taken
lesser than what is permissible as per IS : 456-1978* because the bottom plug
involves mass concreting which is done under-water. It may be taken from 1/6 to
1/10 of the ultimate crushing strength of the concrete used for the bottom plug.
*Code of practice for plain and reinforced concrete ( third revision ) .
TABLE 4 VALUES OF «* AND jg
( Clause 4.7.3 and Note 1 in Table 3)
Length/Breadth 1 1'2 1*4 1'6 1*8 2
Ratio of Mono-
lith's Pocket
0*051 0*064 0*073 0'078 0*081 0*083 0*083 0*083
0*048 0*063 0*075 0*086 0*095 0*102 0*119 0*125
the design of the cover slab. It shall be designed as a conventional slab, in
accordance with IS : 456-1978*.
4.8.2 The level of the cover slab is decided on the basis of the depth
required for the service galleries and the superstructure construction. It is
normally kept just above the low water level.
*Code of practice for plain and reinforced concrete ( third revision).
19
IS : 9527 ( Part I ) - 1981
4.9 Superstructure — The design of the superstructure involves the design
of all components which are constructed above the cover slab. The super-
structure may consist of fascia wall, service galleries, bollard blocks, gap
slabs between adjacent monoliths, arrangements for mooring rings and
fenders, ladders, crane beams, pavements, and any other special features
as required over a particular monolith.
These shall be designed as per the recognised design practices. The
structural soundness and the stability of individual elements, as well as of
the whole system with the monolith, shall be ensured while designing the
superstructure.
4.10 Monolith with Cantilever Relieving Platform
4.10.1 The cantilever relieving platform is used when there are excessive
overturning moments due to deep layer of soft soils and heavy surcharges.
A cantilever, as shown in Fig. 7 is built on the landside of the monolith
at a designed depth. This shadows the earth pressure on the monolith
and also exerts moment opposite in direction to the overturning moment
caused by the earth pressure and mooring forces. Since it relieves the
pressure on the monolith structure, it is called relieving platform.
4.10.2 The depth at which the cantilever should be built, and its span
depends upon the amount of relief required on the structure. The cantilever
may be designed as a reinforced concrete structure conforming to IS : 456-
1978*. However, wherever relieving platform is adopted in design special
attention shall be given by the designer to the sequence of construction
such that it is constructed monolithic with the monolith.
5. STABILITY
5.1 General — The monoliths are invariably designed for heavy lateral
loads in addition to the vertical loads, which are caused due to the earth
pressure, hydrostatic pressure, and the mooring forces (see Fig. 8). The
conditions described in 5.2 to 5.5 in respect of overturning, sliding, bearing
pressure and slip are required to be satisfied to ensure the stability of the
structure.
In case the monoliths are part of a composite structure, rotation of
monolith and its effect may also be examined.
5.2 Overturning
5.2.1 The horizontal forces on the monolith create overturning above
the base. This is resisted by the restoring moment offered by the dead
*Code of practice for plain and reinforced concrete ( third revision ).
20
BOlLARO
DREDGED
LEVEL
CANTILEVER BEAM
EXERTS BALANCING
MOMENT QUE TO THE
FILL ON THE CANTILEVER
RESULTANT LATERAL
FORCE CAUSING OVER
TURNING MOMENT
CANTILEVER BEAM-
SLAB
I >■- " - * ' -*'\\
A — — f '-i — — r ~
* .-• ■ p
* i j * __
w ■' 'r t ».-"■■* p 9
■w * »■ ■ -^.- ■■■•-■ ■'. . y —
■ '.' ■* '• i
* ; ' * ' J
•. .
> ■' -■. . f
...*■- . v ■"*-.. -» ■.•..*.■
SECTION XX
Cft
5°
!
Fig. 7 Cantilever Relieving Platform
IS : 9527 (Part I )- 1981
weight of the monolith, the super-imposed load acting over it, and the
passive earth pressure developed by the soil on the sea-side of the monolith
(see Fig. 8 ).
-BOLLARD
P = Hydrostatic force
W = Resultant vertical force
P\ — Resultant horizontal force
Pu = Resultant active earth pressure
Pp = Resultant passive earth pressure
Pm = Bollard pull
Fig. 8 Forges on a Monolith for Calculation of
Stability Against Overturning
22
IS : 9527 ( Part I ) - 1981
5.2.2 The factor of safety against overturning shall be not less than 1*5
when dead load, live load and earth pressures are considered together
with seismic forces. When dead load, live load and earth pressure only
are considered, the factor of safety shall be not less than 2.
Note 1 — Due allowance shall be made for buoyancy of the submerged portion
of the monolith and the filling.
Note 2 — The exact evaluation of passive earth pressure is still an indeterminate
feature. It develops to the full extent only after the monolith has moved considera-
bly. It has been noticed by experiments that to develop the full passive pressure,
the bulkhead had to deflect by about 2 degree. It has been observed that half
the maximum passive earth pressure is developed even when the movement is
insignificant. Monoliths are invariably very rigid and massive and are not likely
to deflect to mobilise full passive earth pressure; therefore, a reduction factor
0*5 may be adopted in computing the passive earth pressure.
5.3 Sliding
5.3.1 The unbalanced horizontal forces on the monolith tend to slide
it on the founding strata. It shall be ensured that the structure is sufficiently
safe against slidings. Resistance to sliding is offered by friction at the bottom
of the monolith and the passive resistance of the soil on the sea-side of the
monolith. While calculating the lateral forces causing slide, the hawser-pull
shall also be taken into account.
5.3.2 The factor of safety against sliding shall not be less than 1*5, that is
ft*- 5
where
F r = resultant lateral force resisting in slide, and
F a = resultant lateral force tending to slide the monolith.
5.3.3 If the monolith is founded on a sloping rock, it shall be suitably
anchored at founding level to avoid any sliding, by means of dowels, bench-
ing or any other suitable means.
5.4 Bearing Pressure
5.4.1 Design shall be based on permissible bearing pressures established by
detailed soil investigation and tests and previous experience. In deciding
the permissible bearing pressure, the following shall be considered :
a) The safety factor against shear failure shall be not less than 2*5.
b) Settlements under allowable bearing pressure shall not exceed
the tolerable limits.
c) The effect of the skin friction on the monolith shall not be
taken into consideration while working out the bearing stresses
on the founding strata.
23
IS : 9527 ( Part I ) - 1981
5.4.2 The maximum and minimum pressure at the base of the monolith
( see Fig. 9 ) shall be worked out as:
A ^x \,y
where
P = permissible bearing pressure,
R = resultant vertical load,
A = area of the base of the monolith,
Ai x , My = resultant moment in x and y directions, and
Z*> Zv — section modulus of the monolith in x and y directions.
For a rectangular monolith, the above expression works out to
the following:
A \ ~ L ± D )
where
P, R and A are same as described above;
e X) e y — eccentricity of the resultant force R in x andy directions;
and
Ly D = dimensions of the monolith in plan, L being the width
and D, the depth ( see Fig. 9 ).
5.4.3 The maximum bearing pressure exerted on the foundation soil
beneath the wall base, which will be usually at the toe, shall not exceed
the safe bearing capacity appropriate to the foundation soil. A factor of
safety of 2 is adequate to determine safe bearing capacity.
5.5 Stability Against Slip — In some cases, the monolith is founded on stiff
clay. In such cases, if the soil on the back of the monolith is predominantly
soft clay which is deficient in cohesion and internal friction, it is probable
that the monolith, the back side soil, and the underlying strata may slip
as a unit. The stability against such slip shall be checked and a factor of
safety of not less than 1*5 be maintained. For temporary loading conditions
or where the stability reaches a minimum during construction or for extreme
combinations of loading, safety factor may be reduced to 1*2.
6. CONSTRUCTION
6.1 Zones of Monolith
6.1.1 The monolith is differentiated into three zones as described below
{see Fig, 10):
a) Zone I above high water level ( HW ) or above the mean high
water springs ( MHWS ) ;
24
D X
on
9A AXIAL LOAD AND MOMENT
Fig. 9 Calculation of Bearing Pressure
9B EQUIVALENT AXIL LOAD AND MOMENT g>
^1
5
to
00
IS : 9527 ( Part I ) - 1981
yHW OR MHWS
f
■
v.
>
ZONE 1
?
«
.»
ZONE t
■ ■•■
.r
^LW OR MLWS
■f •
'■!•
J
f
*,
t .
t
■' f '
t
9
> .'
*'■
9
ZONE 11
•
t
■'
1-
yU.
9
1 — $_J^
L
DREDGED
LEVEL
Fig. 10 Construction Zones of a Monolith
b) Zone II between HW or MHWS and low water ( LW ) or
mean low water springs ( MLWS ), in other words, between
high and low tide spring tidal range; and
c) Zone III below the low water ( LW ) or mean low water
springs ( MLWS ).
In these three zones, varying requirements should be established
as to the quality of concrete and reinforcement. The design and location
of construction joints also need special attention depending upon the
special local conditions.
26
IS : 9527 ( Part I ) - 1981
6.1.2 In Zone II, the minimum grade of concrete shall be M200, with a
minimum cement content of 370 kg/m 3 . No construction joints shall be
allowed in the zone from 600 mm below LW ( MLWS ), to 600 mm above
the HW ( MHWS ). Where usually severe conditions of abrasion are
anticipated, such parts of the work shall be protected by suitable coatings
or stone facings.
6.2 Spacing
6.2.1 Monoliths shall be constructed as isolated units, separated by
some distance from adjacent monolith. The sinking and grabbing inevitably
cause tilt and shift; therefore, adjacent monoliths shall be so spaced that
there is no adverse influence on either of them due to tilt and shift. If the
monoliths are spaced very close, the soil confined in between the gap of
the monoliths may get compacted and make the sinking difficult. On the
other hand if the spacing is too large then the closure of this gap with the
construction of diaphragm wall may work out to be very uneconomical.
A compromise between these conflicting factors is, therefore, required
while deciding the spacing. It is recommended that the monoliths are
spaced not closer than twice the thickness of the outside steining.
6.2.2 Sometimes notches are left in the side walls of the monoliths to
accommodate diaphragm walls to close the gaps between them. This
system would invariably be unworkable as the monoliths go out of position
due to tilt and shift.
6.3 Placing of Kerb
6.3.1 The kerb of the monolith may be cast slightly away from the final
location of the monolith to take care of anticipated tilt and shift. The
extent of this displacement depends upon the actual site conditions and
experience. Generally, it is cast landwards of the actual location to obviate
the necessity of shifting the fascia-line seaward in case of sea-ward tilt/shift.
In case of land-ward tilt/shift the superstructure can always be built up
to the designed fascia-line.
6.3.2 At sites where the ground level is higher than the designed cut-off
level of the steining, it shall be excavated to avoid excessive skin friction.
The excavation may be done up to 1 50 mm above the subsoil water table.
If the existing soil is weak, a layer of murrum may be spread and compacted
over it such that the kerb can be laid.
6.3.3 If the site of construction is submerged under water, but the depth
of the water is not more than 5 m or so, sand-island may be formed at the
site by dumping sand. The sides of the island should be at least three-times
the sides of the monolith for ease of construction. When the depth of water
and large tidal variations make the formation of sand-island uneconomical,
the use of floating caissions is resorted to.
27
IS : 9527 ( Part I ) - 1981
6.4 Sinking of Monolith
6.4.1 The monolith is sunk as a single unit by dredging the bed
material below the cutting edge. The dredging may be done manually or
mechanically but is usually done by grabs operated from derricks or cranes.
In hard strata, straight chisels may be used to break the material, which
is then taken out with the help of grab. The divers may also be employed
to sink the monolith through hard and difficult strata. They may use water
jets or pneumatic tools to do the excavation and clear the cutting edges.
Whether the sinking should be done by divers or grabs, depends upon the
following factors:
a) Initial cost of equipment,
b) Availability of divers,
c) Overall cost of sinking,
d) Required speed of sinking, and
e) Safety during sinking.
6.4.2 The kerb of the monolith shall be allowed to set for at least a week
before the sinking is commenced. In the early stages of sinking, the monolith
is very unstable because it has very little grip in the surrounding strata.
The chances of tilting increase considerably if the monolith is made top
heavy by raising the steining too high in early stages. In the beginning it is
advisable to let the kerb sink without raising the steining above it. The
steining may then be raised by about 1*0 to 1*5 m at a time and sinking
continued by allowing it to set for at least 24 hours. The setting time
should be increased to 3 days if the surrounding soil and the sub-soil water
contain deleterious materials which are likely to attack the fresh concrete.
Once the monolith has acquired a firm grip in stiff strata, the steining
may be raised more than 1*5 m at a time as it assists sinking.
When the monolith is in the vicinity of founding stratum, the raising
of steining should be restricted so that any variation in the founding level
due to site conditions is taken care of without breaking the already cast
steining.
6.4.3 To ensure the verticality of the monolith, it is essential that the
steining is constructed as straight as possible. During the course of sinking
the monolith tilts and the steining does not remain in plumb. If each lift
of concrete is raised vertically, the final shape of the steining will come out
zig-zag due to which the sinking may become impossible at some stage.
It shall, therefore, be ensured that plumb bobs are not used for raising
the steining.
6.4.4 The main equipment required for the sinking of the monolith
includes grabs, chisels, sand pumps, dredgers, clay and stone cutter, helmets
for divers, cranes, derricks and shearlegs. In the hard strata, heaviest
possible grab and chisel which can be operated in the pocket of the monolith,
28
IS : 9527 ( Part I ) - 1981
is recommended to be used. Special rock cutting teeth may be added to
the grab while sinking through very hard strata.
6.4.5 The monolith sinks by its own weight when the soil below the
cutting edge is removed. Kentledge will have to be added to achieve sinking
when the skin friction due to the external soil is so large that the monolith
is unable to sink under its own weight. Dewatering of the monolith may
also be done where the sinking is not possible even with the help of the
kentledge. Sometimes, this activates sand-blow resulting in sudden drop
of the monolith. This sudden drop cannot be controlled and invariably
causes excessive tilt/shift. Care shall therefore be exercised not to depress
the water level excessively.
6.4.6 If the addition of kentledge and dewatering does not produce the
desired results, air and water jets are used to reduce the friction on the
sides. If such problems are envisaged at the time of designing the monolith,
suitable passages for water, air or mud (bentonite) may be left in the
steining and nozzles permanently fitted at suitable locations.
6.4.7 If all other methods fail, restricted blasting may be permitted.
A very controlled blasting, with appropriate explosive, may be allowed
ensuring that no damage is caused to the existing structures. No divers
should be allowed to work in the nearby monoliths when the blasting is
done. In case of monoliths with two or more pockets, all pockets shall be
subjected to simultaneous explosion so that the monolith does not sink
unevenly.
6.4.8 To achieve sinking in stiff soils, invariably the cutting edge has
to be undercut. This loosens and disturbs the soil around the monolith.
6.5 Tilt and Shift
6.5.1 The tilt and shift occur in every conceivable direction. Up to
certain limits, the tilts and shifts are always permitted and their influence
on the stability of the monolith is taken care of in the design. The limit
is decided by the designer on the basis of his experience and the soil condi-
tions. Whenever, a monolith has tilted beyond the permissible limit, its
stability shall be rechecked and suitable remedial measures, if required,
should be taken before the bottom is plugged. The cumulative effect of
tilts and shifts on a number of monoliths forming a waterfront structure,
invariably alters the originally decided wharf line. This affects the span
between the adjacent monoliths, shifts the position of the fixtures and neces-
sitates the redesign of the superstructure.
6.5.2 Usually the combined effect of tilt and shift should not be more
than ± 300 mm at top of the monolith. Shifts up to ± 300 mm and tilts up
to 1 : 60 depending upon the soil conditions and the size and depth of the
monolith, are permitted. These limits may however be taken as a guide
and be decided as per site conditions.
29
IS : 9527 ( Part I ) - 1981
6.5.3 The tilts and shifts usually do not occur suddenly. The movement
may be observed when the monolith is about a metre above the level of a
comparatively harder strata. This is the time for taking effective measures
to prevent its occurrence. If adequate precautions are not taken to rectify
the tilt and shift at the time it starts, it gets aggravated.
6.5.4 The tilt/shift may occur due to various reasons, a few of which
are described below:
a) Efforts to rush the work in early stages when the monolith
has not even obtained the desired grip in the stiff strata.
b) When too radical steps are taken to correct minor tilts and
shifts.
c) Due to the unequal grabbing from the pockets of the monolith —
simultaneous and equal grabbing should be carried from the
pockets symmetrical about the axes of the monolith.
d) When the monolith enters a harder strata from a comparatively
softer strata — tilting gets further aggravated if the harder
strata happens to be sloping.
e) Occurrence of sand-blow.
f ) When the strata being penetrated is having uneven bearing
capacity.
g) Due to the presence of underground obstruction falling under
a part of the cutting edge.
6.5.5 Methods of Rectification — The methods to rectify the tilt depend
upon the magnitude of tilt, type and depth of soil surrounding the monolith,
the size of the monolith, the availability of resources and the time, and the
most important the ingenuity of the site engineer. Some of the methods
which are commonly used, individually or in combination with each
other, are listed below:
a) Eccentric loading — The higher side of the monolith is provided
with a cantilever platform and loaded with kentledge; this is
accompanied with eccentric grabbing, that is removing the
material from the higher side only.
b) Eccentric grabbing.
c) By pulling or pushing the monolith.
d) By arresting the movement of the lower kerb of the monolith —
this can be achieved by packing the lower portion of the
monolith with sand-bags or hard wooden-blocks, and then
continuing the grabbing operation on the higher side. The
sand-bags/wooden-blocks are removed once the monolith
attains the desired verticality.
e) By jetting water under pressure through the pipes provided
in the steining during its casting — jetting will loosen the
dense sands at the cutting edge and will reduce skin friction
on the exterior wall.
30
IS : 9527 ( Part I )- 1981
f) By chiselling or blasting the stone/boulder which might be
obstructing the edge by sending a diver.
6.6 Construction of Bottom Plug
6.6.1 The bottom of a monolith is plugged with concrete using tremie
process or skip boxes, or by colloidal concrete. Any of the methods may
be adopted ensuring that sound concrete is obtained, and in no case the
concrete is dropped from a height. If the concreting is done using skip-
boxes, adequate arrangements should be made such that they distribute
the concrete evenly at the base.
6.6.2 The bottom of the monolith shall be thoroughly cleaned of sand
and other loose materials before the commencement of plugging. Accurate
sounding shall be taken and recorded to ascertain the depth of various
points in the pocket/pockets. Founding of the monolith is always difficult
on sloping or uneven rocky bed. Under such circumstances, it may become
necessary to blast the rock or do underpinning to support the steining
adequately. Sufficient soil/rock samples obtained at the founding level
shall be kept for inspection and record.
6.6.3 The water in the pockets of the monolith shall be still and up to
its normal level before the plugging is commenced.
6.6.4 The plugging shall be done in one continuous operation till com-
pleted. If there are two or more pockets, the plugging shall be done simul-
taneously and to equal heights in all the pockets.
6.6.5 It has been observed that the concrete used for the bottom plug
takes longer time to set and considerable proportion of cement gets washed
resulting in weak concrete; therefore, 10 percent extra cement shall be
mixed in the concrete.
6.6.6 There shall be no flow of water through the concrete till it is set.
6.6.7 Testing of Bottom Plug — The soundness of the bottom plug may be
tested by dewatering the monolith by 5 m below the surrounding ground
water-level, and checking the rise of water. The rate of rise shall be less
than 100 mm per hour and in case it is higher, suitable remedial measures
shall be taken. The test shall not be done earlier than 21 days after con-
creting of bottom plug.
6.7 Filling
6.7.1 The pockets of the completed monoliths are generally backfilled
with approved sand. The sand filling cannot be relied upon for transmitting
the weight of the superstructure to the bottom plug. The main contribution
of the filling is to improve the stability of the monolith, and eliminate the
31
IS : 9527 ( Part I ) - 1981
development of tension at the base which may be caused due to over-
turning moment. The stresses in the steining due to outside earth and
hydrostatic pressures are partly reduced by the filling.
6.7.2 The filling, though helps in the stability of the monolith increases
the bearing pressure on the founding strata. If the bearing pressure is likely
to increase beyond the acceptable limits, the monolith may not be back-
filled provided the monolith is stable otherwise.
6.8 Expansion Joints
6.8.1 The quay wall solidly built with monoliths should be provided
with expansion joints so that they can absorb the movements arising from
shrinkage, temperature changes and yielding of the foundation. The normal
length of the sections between the expansion joints is 30 m; however, it
is left to the discretion of the designer in view of the large number of factors
involved in deciding the location.
6.8.2 The expansion joints in the sections are keyed for mutual horizontal
support. These shall be so provided that the necessary movement occurs
with a minimum resistance at the joint. Reinforcement shall not extend
across the expansion joint and the break between the sections shall be
complete. These shall also be covered vertically in such a way that the
backfill is prevented from being washed out.
6.9 Construction Joints
6.9.1 There shall be no construction joints in the tidal zone ( see 6.1.2 ).
The construction joints shall be so placed in the outer walls that no shrinkage
cracks may possibly occur. The steel reinforcement shall also be so designed
that it prevents the occurrence of shrinkage and temperature cracks; but
making a special mesh for the purpose is unnecessary. For guidance on
providing the construction joint, requirements of IS : 456-1978* shall be
followed.
6.10 Facing and Nosing
6.10.1 Facing of the concrete may be omitted if the steining and the
superstructure is well designed and satisfactory concrete is used. If a facing
is required as a protection against unusual mechanical wear, the use of
basalt, granite or equivalent is recommended. A hard concrete coating
about 50 mm thick is also considered suitable as a wearing surface along
the coping of the water front structure, but is only required if there is going
to be heavy traffic and the vessels are moored with steel hawsers.
6.10.2 The fascia wall is constructed vertically and is generally given a
chamfer of about 150 mm at the upper edge or is correspondingly rounded
off when a special nosing is not used. When nosing is installed for the
protection of the wall, and as a safety against slipping of the line handlers,
it shall be so constructed that the surface water easily drains off.
♦Code of practice for plain and reinforced concrete ( third revision ).
32
IS : 9527 ( Part I ) - 1981
6.11 Precast Structural Elements — Precast concrete structural elements
may be used with advantage for various components of superstructure. Care
shall however be taken for joining them securely with cast-in-situ concrete
for proper transmission of forces. The unavoidable construction joints
often occur at such locations where the stresses are high. In such cases
the joints shall be carefully designed and constructed.
33
INDIAN STANDARDS
ON
PORTS AND HARBOURS
IS:
4651 ( Part I )-1974 Code of practice for planning and design of ports and harbours:
Part I Site investigation (first revision )
4651 ( Part II )-1969 Code of practice for planning and design of ports and harbours:
Part II Earth pressures
4651 ( Part III )-1974 Code of practice for planning and design of ports and harbours:
Part III Loading (first revision )
4651 ( Part IV )-1979 Code of practice for planning and design of ports and harbours:
Part IV General design considerations (first revision )
4651 ( Part V )-1980 Code of practice for planning and design of ports and harbours:
Part V Layout and functional requirements
7314 - 1974 Glossary of terms relating to port and harbour engineering
9527 ( Part IV )-1980 Code of practice for design and construction of port and harbour
structures: Part IV Cellular sheet pile structures
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